The present invention relates to a railway vehicle operation-control system and a railway vehicle using the operation-control system so as to achieve a target operation by using a plurality of drive devices.
A railway vehicle and an airplane runs or aviates by operating a plurality of power-driven apparatuses which are connected in parallel. For example, a railway vehicle is composes of several or over ten rolling stocks. Each rolling stone usually includes 3 or 4 inverter drive-apparatuses. Further, about 2-4 motors are connected to each inverter drive apparatus in parallel. Also, each inverter drive-apparatus receives a torque-output instruction sent from an operation unit provided at the top rolling stock, and is controlled so that an actual torque-output is equal to the instructed torque-output, by controlling each motor current.
Conventionally, the running of a railway vehicle is performed as follows. A torque-output instruction is allocated to each inverter drive-apparatus from the operation unit, and several kinds of artifices are applied to the allocating of the required torque-output to each inverter drive-apparatus. A railway vehicle runs on a railway made of iron, using wheels made of iron, while being accelerated or decelerated. Since the friction coefficient is small, an iron wheel tends to cause idle running. Also, since the friction coefficient of iron changes depending on surface states of a railway and wheels, the friction coefficient is affected by wet or rusty sates of the railway and the wheel.
The top rolling stock particularly tend to receive effects of the surface states of the railway, which in turn easily causes idle running. Accordingly, the torque generated by the top rolling stock is set to 80-90% of the torque of the consecutive rolling stocks. Further, the friction force is proportional to the load applied to a contact face between a wheel and a railway.
Therefore, for a rolling stock in which there are a small number of people, a way for preventing idle running by reducing the torque of this rolling stock is performed. Even if a trouble of idle running occurs, each drive device is controlled so that the idle running of each drive device is prevented by reducing its torque, and the torque of each drive device is gradually returned to its predetermined torque.
Further, an inverter is heated by a current conduction loss when current flows in the inverter, and a switching loss when current switching is operated. If the temperature of an inverter element increases to more than a design value, the element breaks down by heat. Therefore, the increasing values of switching elements are estimated based on a running pattern of a rout on which the railway vehicle is to run, and the temperature characteristics of the switching elements. By using the results of the estimation, the electric characteristics of the switching elements and the cooling performance of cooling devices to be used are designed so that the switching elements does not break down even at the worst case. The worst case is that wind does not absolutely pass around the cooling devices, or that the number of riding people is more than a limit value.
A car is a system driven by a method similar to that of a railway vehicle. In a car, a torque-output fed from one power source is optimally distributed to each wheel by a mechanical power distribution apparatus while being adaptive to surface states of the road, in order to improve the operational performance.
The present invention aims at a system in which a plurality of power sources are connected in parallel. Accordingly, the present invention does not aim at a system, such as a car, in which there is one power source, and which is well driven by adjusting transmission coefficients of a transmission device for transmitting drive force from the one power source to wheels.
A conventional railway vehicle system is designed so that a break down trouble does not occur even at the worst case, assuming the worst case determined based on actually measured or experienced data. Further, even if any trouble occur, each problem device is separately treated. However, if each problem device in a system is independently treated, there are several problems in a such conventional system.
For example, in an idle running, the following problem will occur. At first, The torque to the idle-running wheel is reduced, in order to stop the idle running, and the torque to the wheel is returned to the predetermined torque after the idle running has stopped.
However, since each device is separately treated, if an idle running occur, the acceleration ability of the whole railway vehicle is deteriorated.
Further, in a heating problem of an inverter, the following problem may occur. In a recent inverter, a switching element is made of semiconductor. Since a heating loss of a semiconductor switching element increases as its temperature become higher, it is desirable to use a semiconductor switching element at a low temperature. In A large system such as a railway vehicle whose length is about 300 m, the temperature of each inverter is different due to its environmental conditions such as natural window, raining, etc. If each device is operated at the same allocated torque instruction (not controlled), the inverters, whose temperature are high, cause a large quantity of loss, and their temperature more increase, which in turn degrades the energy conversion efficiency of the inverters.
An objective of the present invention is to prevent the degradation of a large system such as a railway vehicle.
Another object of the present invention is to maximize the energy conversion efficiency by minimizing the loss of the inverters.
To achieve the above objectives, a railway vehicle of the present invention includes; at lest one monitoring unit, provided at devices, which performs a monitoring function for monitoring an operational state of each device; a communication network; a central processing unit for optimally distributing control information to each device.
The monitoring units acquire information on operational states of the respective devices, and sends the information to the central processing unit via the communication network. The central processing unit calculates a difference between a permissible level of a state variable such as torque, temperature, etc., and a current level of the corresponding state variable, for each device, and allocates a controlled-variable to each device so that each difference is larger than a predetermined permissible value. Further, if the current controlled-variable level (power-output) of some device exceeds its predetermined permissible level, the controlled-variable of this device is reduced, the amount of reduced controlled-variable is distributed to the rest devices. The controlled-variables of the rest devices are adjusted, and are allocated to respective devices via the communication network. That is, the rest devices are controlled based on the controlled-variables redistributed by the central process unit. Here, a permissible value (level) of each device is determined by using data measured in advance, or can be changed based on the monitoring results of the monitoring device for each device.
If an idle running trouble occurs, the control processing of this trouble is explained as follows. The state of torque of each inverter, and the state of each idle-running place, are periodically transmitted to the central processing unit via the communication network. When the central processing unit receives the information on occurrence of the idle running trouble from some monitoring device, the central processing unit immediately reduces the torque of the problem inverter related with the idle running trouble, and sends the instructions of reallocation of the reduced torque to the rest inverters. In this allocation, the reduced torque is allocated so that each allocated torque is less than the maximal torque value at which an idle running occurs at each device. Each maximal torque value causing an idle running is a predetermined value which was predetermined by actual measurement data in advance, but this maximal torque value is adjusted by taking the railway conditions of xe2x80x9cnew or oldxe2x80x9d, the surrounding environment such as climate, the total weight of each rolling stock, etc., into account, and it is possible to flexibly adjust each maximal torque, and to more appropriately determine the reallocation to the rest inverters. In some situation of occurrence of an idle running, it is also possible to change the maximal torque of each wheel in turn.
The control processing for the inverter temperature is explained as follows. The temperature of a semiconductor switching element of each inverter is sequentially measured, and the measured temperature value is transmitted to the central processing unit via the communication network. The central processing unit reduces the current flowing in the inverter of the high temperature so as to reduce the torque generated by this inverter, and reallocates the reduced torque of the devices connected to the rest inverters so that the temperature of the inverters is almost equal. If the above reallocation of the reduced torque in the rest inverter is not impossible for a predicted necessary acceleration performance, the drive conditions of the semiconductor switching elements are changed so that the loss of the switching is reduced. If such drive conditions cannot be found, the acceleration level of the railway vehicle is decreased.
Thus, in the present invention, a permissible value is always compared with a current controlled-variable (power-output) of each device, and the difference between the permissible value and the current power-output, which is defined as a performance margin, in this specification.